Ferromagnetic alloys of the cobalt/rare-earth type have a high energy product and for this reason have been widely used. At present they are generally fabricated by powder metallurgy, i.e. by sintering, high-pressure pressing or the like techniques. For example, powders of rare-earth/cobalt can be sheathed (enrobed) in a tin alloy and compacted or shaped therein. The alloys generally have the formula TRCo.sub.y, where TR is a rare-earth element such as samarium (Sm), gadolinium (Gd), praseodymium (Pr), cerium (Ce), neodymium (Nd), holmium (Ho) or an element similar to a rare-earth such as lanthanum (La) or yttrium (Y) or a mixture of such elements. y varies between 5 and 8.5.
Although these materials are remarkable for their magnetic properties, having a high intrinsic coercive force of, say, 25 kiloOersted (kOe) and a high saturation magnetization of, say, 10 kiloGauss (kG), resulting in a high energy product, they are fragile, difficult to work and sensitive to environmental conditions. Because of these shortcomings, the fabrication of small magnets by machining is difficult. When attempts are made to fabricate large magnets, it is found that the bodies tend to break during fabrication because of internal stresses.
Alloys containing copper as well as TRCo.sub.y which are prepared by casting have also been proposed heretofore. These alloys are subjected to a magnetic hardening treatment but are also found to be very brittle and difficult to work, particularly by turning and similar machining operations.